Measuring internal temperature inside a sealed cell of an atomic magnetometer using steady-state linewidth analysis

We report a non-destructive and in-situ measurement technique to infer the internal temperature inside a sealed cell of an atomic magnetometer, based on steady-state linewidth analysis. This approach exploits the relationship between the alkali vapor density and the steady-state linewidth of the magnetometer in the presence of an applied DC magnetic field, particularly when the spin polarization of the alkali metal is significantly low ($P\ll 1$). The atomic density inside the cell is a univariate nonlinear function of the cell temperature, enabling us to establish a model linking the magnetometer’s steady-state linewidth to the internal temperature of the cell. To validate the accuracy and feasibility of this method, we conducted a series of experiments over a wide temperature range, from 140 °C to 190 °C. Using the magnetometer’s steady-state linewidth as a key parameter, we successfully measured the actual temperature inside the cell. The test results were corrected to ensure precision and reliability, and comprehensive evaluations of measurement uncertainty were performed to quantify the confidence level in the temperature measurements. This novel determination method marks a significant advancement in atomic magnetometer temperature measurement, offering real-time and on-site monitoring capabilities within sealed cells.